The present invention relates to heatsinks. More particularly, the present invention relates to surface mount heatsink elements on printed circuit boards.
As circuit board components require more power, some of the surface mount devices (SMDs) have become more dependent on using the printed circuit board (PCB) as a primary thermal path to a heat sink. Typically, the SMD relies on a copper pad upon which it is mounted and upon thermal vias to help carry away the thermal energy generated during operation through the layers of the PCB. FIG. 1 illustrates a SMD disposed on a PCB in accordance with the prior art. A PCB 102 has a first copper pad 104 disposed on one surface, and a second copper pad 106 disposed on the opposite surface. Thermal vias 108 thermally connect the first copper pad 104 to the second copper pad 106. A SMD 110 is mounted on the first copper pad 104 such that the SMD 110 is thermally coupled directly to the first copper pad 104. The heat generated by the SMD 110 dissipates through the first copper pad 104, down through the thermal vias 108, and through the second copper pad 106.
However, the PCB 102 provides a relatively poor thermal path to dissipate the heat generated by the SMD 110. The copper pads 104 and 106 and the thermal vias 108 provide poor air exposure and poor thermal paths. One solution involves increasing the effective copper pad surface by expanding the surface area of the copper pads 104, 106 relative to the SMD 110 such that a greater surface area on the copper pads 104, 106 is exposed to air. However, that solution would require more space on the PCB 110 which is usually unavailable.
Another solution involves customizing a heatsink (not shown) on a top surface of the SMD 110. The heatsink is thermally coupled directly to the top surface of the SMD 110. However the heatsink needs to be customized for every SMD used in this fashion since the shape of a heatsink for one SMD may be completely different from the shape of a heatsink for another SMD. Such customization proves to be inefficient and costly.
It would be desirable to provide a PCB capable of efficiently providing thermal paths through scalable thermal conductive elements that flexibly adapt to any SMD shape, thereby saving costs and board space.
A printed circuit board (PCB) has at least a first surface. A patterned electrically and thermally conductive layer is disposed on the first surface. A surface mount device (SMD) is disposed on an area of the layer and is attached thereto with solder. Heatsink elements, each including at least one flat surface, are placed by a pick and place assembly robot and permanently attached to the area with solder.